1. Field of the Invention
The invention relates to a method and apparatus for protecting sailboard fins, fin holders, and board structure from damage in the event that the fin strikes an underwater object.
2. Related Art
Sailboarding since its introduction in the 1970's has become an international sport of major proportions and is considered to be the fastest growing water sport in the world. Sailboards are used in conditions ranging from a slight breeze on a calm lake to gale force winds in rough ocean surf.
A sailboard usually consists of a substantially flat, elongated board, a sail system, an optional centerboard system, and a fixed fin mounted aft. Much of the design of the sailboard has been borrowed directly from surfboards, including the fixed fin.
The fixed fin is fastened to a fin holder, the fin holder being permanently molded or fastened into the sailboard. This combination of fin and fin holder allows the fin to easily be installed and removed.
Because of the versatility and shallow drafts of sailboards, these craft are often sailed in areas where the aft mounted fin will come into contact with an underwater obstruction, such as rocks, reefs, underwater debris, or the bottom of the sailing area. Damage due to the fin striking an underwater object may result in the following:
1. Breaking of the fin
2. Breaking of the fin holder
2. Delamination of the fin holder from the board structure
4. Damage to the sailboard
5. Any combination of the above
Replacement or repair of the damage described above is in most cases very costly. It is therefore highly desirable to fasten the fin to the fin holder in such a manner as to protect the fin and more expensive fin fastening components from damaging overloads.
U.S. Pat. No. 4,398,485 by Bernard Diziere for DEVICE FOR DETACHABLY SECURING A CENTERBOARD TO A SAILBOARD OR THE LIKE has a similar object as the present invention, to protect the fin and sailboard from damage when the fin hits something. Diziere illustrates the need for this type of protection. Himmer, Diziere completely replaces the standard fin holder with an incompatible fin non-industry fin holder.
Reference is also made to my previous U.S. Pat. Nos. 4,846,795 and 4,964,826, as well as the art cited therein, wherein members which fail under impact are disclosed.
A nylon screw has been used between the outside of the board assembly and the fin. The purported purpose of the screw has been to fail under impact. However, the basic problem with this approach is that the nylon screw is too weak to function during normal use because a nylon or similar type screw cannot stand-up during normal tightening of the fin and/or under steady state loads incurred in normal sailing conditions.
References should be made to German Offenlegungsschrift DE 3043496 which discloses a tether in the form of flexible or elastic cord.
The generic term for this type of fin holder is: "Through the Deck Fin Box." This term is derived from the fact that the fin fastening screw is inserted through the deck of the board.
The through the deck fin box was developed to provide the fin with increased lateral support, as compared to adjustable fin boxes. The increased lateral fin support is due to the increased depth of the holder. Another advantage of this type of fin holder is the decreased hydrodynamic drag due to the fin completely filling the open cavity of the fin holder when installed as well as the lack of a fastening screw at the open end of the holder. A distinct disadvantage of this type of fin holder assembly is the lack of adjustability.